In battle terms, the only thing the Nursery Spider offers over any other Spider, is the replacement of its "primary" ability - from Strike (Beast) to Skitter (Critter). Considering that it only comes in "hybrid" */B breeds, I don't think it'll shine in any particular circumstance (unless you direly need Webbed for some reason).

Do we have a confirmation somewhere on all of its breeds?I dropped 2k gold on them trying to get something other than S/B... all of them turned out to be S/B...

Very possible that all are S/B indeed. On the lowest levels, stats of pets are too low to be sure which breed they represent. Addons either suggest all options possible (BPBID) or attempt to guess only one that may turn out to be false.

Do we have a confirmation somewhere on all of its breeds?I dropped 2k gold on them trying to get something other than S/B... all of them turned out to be S/B...

I'm unsure, mine was S/B too but the addon lists P/B as a possibility - although either way, it fails to recognize them at L1. My guess is that all of them are S/B, but its not something I can confirm :3